Month: May 2016

Do the buildings you manage have lightning protection?

Lightning protection acts as a safeguard, it’s designed to protect a structure by intercepting extremely high currents of strikes and passing them safely from the structure to the ground, via a network of air terminals, conductors and ground electrodes.

Without lightning protection, you as a property owner or facilities manager may be putting occupants at risk. Not only protecting a building’s structure, contents and surroundings should be of priority, but also the tenants within the building.

What are the Australian Standards for Lightning Protection?

To decide the level of protection required for any building, you must first determine the type of building it is and its contents. In all cases, lightning protection is required to provide protection for personnel within any building. Additional protection may be required if what is located inside the building as classified as ‘sensitive equipment.’

What are the Building Type requirements?

Type I Building is defined as a building with metal cladding on the roof and all walls. Lightning can strike the building and it will flow to ground, via the cladding. The steel framed, reinforced concrete buildings with metal cladding provides almost total protection. The cladding acts as both an air terminal and down-conductor (the cladding must be connected to the earthing system). A building without electronic equipment and basic surge protection e.g. main switchboard surge diverters and telephone protection on MDF is necessary.

Type Ia Building is similar to type I, except it contains electronic equipment and associated equipment: outdoor antenna, sensors, etc. In this case full protection is necessary and the protection boundaries must be established.

Type II Building is constructed from reinforced concrete or steel framed with no metal cladding. All steel frames must be connected together and bonded to the roofing if it’s metal. The steel frames may act as the down-conductors.

Type IIa Building is similar to type II, except it contains electronic equipment and associated equipment: outdoor antenna, sensors, etc. In this case full protection is necessary and the protection boundaries must be established.

Type III Building is constructed from materials substantially free of metal. Down-conductors must be installed externally to the building and earthed to the building earth. A lightning stroke counter should be fitted in at least one down-conductor to measure lightning strike activity. The strike counter should be waterproof with a reset button inaccessible without the use of tools and the unit powered by a long life battery of minimum 10 years.

Type IIIa Building is similar to type II, except it contains electronic equipment and associated equipment: outdoor antenna, sensors, etc. In this case full protection is necessary and the protection boundaries must be established.

For non metallic roofs, apply the rolling sphere analysis method, explained below. The rolling sphere analysis may also be used to design placement of finials of large flat roofs.

(Building Types courteous of Novaris Pty Ltd)

How does a Lightning Protection System protect a building?

The standard Lightning Protection Design endorsed in the AS1768 Standard is based on the Rolling Sphere Methodology. This methodology is said to roll over the whole structure for protection. All areas of the structure that the sphere touches are considered to be exposed to direct lightning strokes, and would need to be protected by the placement of lightning rods, or air terminals.

The diagram below depicts the Rolling Sphere Method (RSM).

In general, air terminals need to be installed in such a way that the rolling sphere only touches the upper surfaces. If the sphere is to touch the outer section of the structure, then additional air terminals should be installed at those points. The values of the rolling sphere radius are based on four protection levels:

Level 1 Protection

20 Metre Rolling Sphere

Level 2 Protection

30 Metre Rolling Sphere

Level 3 Protection

45 Metre Rolling Sphere

Level 4 Protection

60 Metre Rolling Sphere

Some structures are more at risk of being struck by lightning. The risk for a structure is the area size, the height and the number of lightning strikes per year per mi² for the area.

Lightning protectors should be placed where they will prevent the sphere from touching a structure. A weak point in most lightning systems is in transporting the captured discharge from the lightning rod to the ground.

Lightning Protection Systems are used to lessen or prevent lightning strikes from damaging structures. These systems lessen the fire hazard which lightning strikes can pose to structures. A Lightning Protection System provides a low-impedance path for the lightning current to lessen the heating effect of current flowing through flammable structural materials. If lightning travels through porous or water-covered materials, then these materials can explode if their water content is turned to steam by heat produced from the high current. This is an example of why trees can be often shattered by lightning strikes.

What are the main components of a Lightning Protection System?

The parts of a Lightning Protection System consist of:

Air terminals (lightning rods or strike termination devices)

Bonding conductors

Ground terminals (ground or earthing rods, plates, or mesh)

Connectors

Air terminals are placed at or along the upper points of a roofing structure and are electrically bonded together with bonding conductors (down conductors or down leads). These are connected by a direct route to one or more grounding (earthing) terminals. The connections to the earth electrodes must not only have low resistance, but must have low self-inductance.

How does a Lightning Protection System work?

A Lightning Protection System provides a conductive path between an air terminal and earth, so that when a building is struck by lightning, the majority of the lightning’s current follows the path of the Lightning Protection System, with substantially less current traveling through flammable materials.

Damage to a building occurs when high voltages travel too quickly and bypass surge protection equipment. Because lightning can send extremely high voltages into an electrical installation, arcs can jump at multiple places, which can cause mechanical damage and ignition to a building.

Striking a power line or wire fence, then travelling into the building

Can Lightning Protection be installed after a building is constructed?

Installation of a Lightning Protection System should ideally be done during construction as the AS1768 Lightning Protection Standard specifies that the conventional design should be designed and installed during construction, as this type of Lightning Protection System can be difficult to retrofit to existing buildings, and would require down conductors to be installed vertically on the external walls every 20 metres. These conductors also require to be clipped every metre or so, as the system can be visually unsightly and detract from the aesthetics of the building.

During construction, structural rebar within the concrete may be used to carry lightning current to ground where there is a continuity of the rebar from roof to ground. Where this continuity is not assured, the use of dedicated down conductors is recommended.

These systems are very labour and component intensive, where the install costs can be considerable as an overall percentage of the systems cost.

Alternatively, there is another Lightning Protection System which is commonly used, the non-conventional design, although it is outside of the scope of the AS1768 Lightning Protection Standard.

Is lightning protection a legal requirement?

The Australian Standard AS/NZS 1768-2007 ‘Lightning Protection’ provides useful guidance in this respect, and it is recommended that whilst this is not a “mandatory” standard, if the recommendations and design considerations are implemented in their entirety, the greatest level of acceptable protection can be afforded to both equipment and personnel.

The AS/NZS 1768:2007 Lightning Protection Standards Australia provides guidelines for the protection of persons and property from the hazards of lightning. It applies to conventional Lightning Protection Systems consisting of air terminations, down-conductors, earthing systems and surge protective devices. It also provides a comprehensive risk management process for the determination of the risk of damage due to lightning for a range of structures.

This Standard sets out guidelines for the protection of persons and property from hazards arising from exposure to lightning. The recommendations specifically cover the following applications:

The protection of persons, both outdoors, where they may be at risk from the direct effects of a lightning strike, and indoors, where they may be at risk indirectly as a consequence of lightning currents being conducted into the building.

The protection of a variety of buildings or structures, including those with explosive or highly-flammable contents, and mines.

The protection of sensitive electronic equipment (e.g. facsimile machines, modems, computers) from over-voltages resulting from a lightning strike to the building or its associated services.

The nature of lightning and the principles of lightning protection are discussed and guidance is given to assist in a determination of whether protective measures should be taken.

What standards must be met with Lightning Protection Maintenance?

Lightning Protection Systems are sophisticated networks. Not only does weather, such as extreme temperatures and high winds affect lighting protection equipment, but also building upgrades involving new construction, building additions, re-roofing or remodelling and changes to electrical, mechanical or communication systems can also affect a system’s performance.

Because changes are likely if not inevitable, all electrical building maintenance schedules should include annual lighting protection equipment maintenance.

A Lightning Protection Test and Earth Grid Test must be carried out when the installation has been completed and should be done by a licensed electrician. By law, certified testing must occur within a two-year time frame. To ensure thorough and correct maintenance, a Lightning Protection Test checklist should be followed.

A properly designed Lightning Protection System safeguards vulnerable structures, equipment, and trees by providing an easy path to a ground, which harmlessly dispels the electrical charges. Protection should also be provided for objects located where a lightning strike’s current might side-flash, such as electrical wires or metal devices on building roofs.

Installation of a Lightning Protection System must be designed and installed by a professional. Codes and standards must be followed.

Standards Australia has set new building regulations for emergency and exit lighting requirements. Effective January 2016, the new legislation includes the mandatory installation of a new test switch when an existing emergency or exit light is being changed over by an electrician, to a fitting that is not the same type, in the same location and same wattage as the current one; this falls under clause 1.7 of AS2293.1.

AS/NZS 2293 Emergency Lighting for Buildings covers three parts:

Part (i) Installation
Part (ii) Maintenance
Part (iii) Performance of Luminaires

Changes to any part of the emergency and exit lighting standards (AS2293.1) must be implemented by Facility and Property Managers, for building compliance.

Although the changes are substantial, in this article we are covering only manually tested Single Point Systems (the most common type).

Single Point Emergency and Exit Lighting Systems were implemented in the 1990’s. In 2012, emergency and exit lighting became a national standard, following the publication of the AS/NZS 3000:2007 Amendment 2 and AS 2293.1.

What are the changes associated with Emergency & Exit Lighting for Property Managers?

For properties under your management, there are four main changes that will impact the cost of replacing, or installing additional emergency and exit lights. These changes don’t need to be implemented during the six monthly testing, these changes need only apply when:

(i) a new fitting is added, or
(ii) an existing fitting is replaced with a new fitting, that is different from the current one

1. Circuit Monitoring

Circuit monitoring must be applied to an added circuit, or when a fitting is replaced. The intent is to provide lighting when there is a loss of general lighting, to allow a person to vacate a section of the building.

How it worksUpon failure of the electrical supply to any lighting circuit within a building, circuit monitoring will detect that a lighting circuit has been de-energised and will automatically activate the emergency and exit lighting. Once the lighting circuit has re-energised, the emergency and exit lighting will de-activate and return to charging state.

2. Emergency Test Switch

An emergency test switch must be applied to an added circuit, or when a fitting is replaced.

How it worksAn emergency test switch is used as a manual test facility. The buttons on the test switch are used for testing purposes (i.e. enable/disable prolong, set duration time, enable/disable monitoring lines). For six month scheduled testing, the test switch is used to control the emergency and exit lighting without affecting any other part of the electrical installation.

3. Dedicated Emergency & Exit Circuits

Any emergency or exit fitting added or replaced to a circuit, must be on a dedicated circuit for emergency and exit lighting only. If this existing circuit is mixed (e.g. the same circuit as general lighting or power) it must be rewired on a dedicated circuit, back to an emergency test switch.

4. RCD’s for Emergency & Exit Circuits

RCD’s are no longer a mandatory requirement for emergency and exit lighting circuits. In the past if an emergency or exit light was replaced and the circuit was not RCD protected, there were additional costs for installing an RCD.